Fire safety is very important in business or commercial buildings. Methods of achieving fire safety include the proper selection of building materials and equipment with the objectives of preventing ignition of a fire, providing for the prompt detection of the occurrence of a fire and most importantly, designing the building to limit the impact of any fire that occurs. Limitation of a fire's impact is concerned with containing or limiting the spread of a fire and providing for quick extinguishment of a fire with minimal damage to the building and its equipment.
An excellent approach to the limitation of the impact of a fire is through proper design to provide containment to limit the spread of a fire. Containment is achieved through the use of fire stopping barriers which prevent the spread of the fire from one part of the building to another. Walls, for example, are a very effective barrier.
Modern business buildings, however, contain many conduits for electrical cabling which pass through otherwise effective barriers such as floors and walls. These conduits are usually continuous passageways and contain no effective fire stopping barriers. In particular, communication terminal buildings are especially prone to fires since they have many conduits to accommodate extensive cabling.
A fire phenomenon can be described in terms of several, well-defined sequential stages of a fire. The first stage of a fire is usually a smoldering condition. This condition subsequently passes to a second stage comprising an ignition condition and then continues to a third stage, namely, a full flame condition. These stages are often not simultaneously uniform over the entire building. A portion of the building may have a fire in a full flame condition while another part of the building, subjected to a heat energy transfer therefrom, including convective, conductive, and/or radiant energy interchanges may be in a preignition smoldering condition. It is apparent that a full flame fire in one section of a building, through this thermal energy interchange, may cause the start of a smoldering condition in another section of the building.
During this initial smoldering period, smoke and toxic gases are generated which may also travel via convection to other parts of the building unless effective barriers are used. The smoke and toxic gases generated by this smoldering action may cause very extensive damage through chemical reactions to communications equipment and even if the fire itself is suppressed, the damage caused by smoke and toxic gases may be quite extensive.
Standard cabling conduits presently used for communication and electrical cables readily permit the transfer of heat energy, smoke, and toxic gases. The transfer mechanism of convection is well-suited to the open passageway of a conduit which readily permits the spread of smoke and gas from one room to another. The nature of the cabling itself readily permits the conduction of heat energy along the copper core of the cable. This means that the heated copper core may cause smoldering of plastic insulation of the cable in a room otherwise insulated from a fire. This generates smoke and toxic gases which are very damaging to any sensitive electrical equipment contained in the room.
Prior art barrier techniques for cable conduits include the use of perforated barriers allowing the travel of cable from one side to another through individual perforations or holes. In other instances, the cables are transmitted through the conduit in bundles and bags of fireproof material which are stuffed about the cables at the egress point to provide an effective fire barrier. The first technique has limited versatility should the number of cables needed change. The second technique provides a fire seal, but in no way prevents the passage of toxic gases through the interstices of the cable bundle.
Certain desirable characteristics are necessary for a fire retardant conduit structure to be effective in reflecting the needs of fire protection in modern communication terminal buildings. A desirable fire retardant conduit structure should be cost effective. This means the cost of manufacture is low and the structure is easily installed at a low labor cost. The conduit structure should have a simple design and be easily adaptable to any size installation including adaptability to future cable number requirements. It should also be of solid construction which permits it to be repaired and reused after a fire and most importantly, effective at stopping a fire during every phase of the fire process.